When comparing mnamer vs Flexible Renamer, the Slant community recommends Flexible Renamer for most people. In the question“What are the best bulk rename tools for Windows?” Flexible Renamer is ranked 9th while mnamer is ranked 13th. The most important reason people chose Flexible Renamer is:
It has many options, including renaming using tags (ID3, Exif...), can number files, use wildcards or regular expressions, walk a hierarchy of folders. And it has presets for common renaming tasks, like removing parentheses, "Copy (n)" or "Shortcut of", and so on. Its preview feature avoids errors, and warns (a bit late though) of naming conflicts.
Specs
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Pros
Pro Can operate in batch mode or interactively
Pro Works for movies and television media files
Pro Powerful but easy to use
It has many options, including renaming using tags (ID3, Exif...), can number files, use wildcards or regular expressions, walk a hierarchy of folders.
And it has presets for common renaming tasks, like removing parentheses, "Copy (n)" or "Shortcut of", and so on. Its preview feature avoids errors, and warns (a bit late though) of naming conflicts.
Pro Free
Freeware and lightweight (archive is less than 2 MB).
No install, but might need removing options of Explorer integration / scripting if removing.
Pro Context menu in Explorer
Can add a context menu to Windows Explorer to rename files in a chosen folder.
Pro Tag management
Can rename using ID3 (music), Exif (photo), IPTC (images), DOC or HTML tags.
Pro Has many translations
Available in English, Japanese, French, Spanish and German.
Pro Scriptable
You can write scripts in VBScript or in JScript (native Windows scripting languages) for complex renaming operations.
Cons
Con Requires Python to be installed
Con Runs via a CLI interface
Con Seems to be no longer maintained
Last updated in 2011 (v. 8.4). Yet it works fine in Windows 10 and still does a tremendous job.